InstantHMI traps the silk screened buttons on the Palm/Pocket PC (such as Home, Calculator, etc.) and prevents their use while executing InstantHMI application program. The power button (on the Palm)  is trapped by InstantHMI and turning off power is allowed only after Exit from the InstantHMI application to ensure that on going data logging and Trending functions are not interrupted un-intentionally. You may however turn the back lighting on using the Power button on the handheld.